Fluid forces on a square cylinder in oscillating flows with non-zero-mean velocities

• Published in: International journal for numerical methods in fluids Vol. 60; no. 1; pp. 79 - 93
• Main Authors: Chen, Chu-Chang, Fang, Fuh-Min, Li, Yi-Chao, Huang, Long-Ming, Chung, Cheng-Yang
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 10.05.2009; Wiley
• Subjects: Computational methods in fluid dynamics; Exact sciences and technology; Fluid dynamics; Fundamental areas of phenomenology (including applications); Hydrodynamic waves; large eddy simulation; Morison equation; Physics; Rotational flow and vorticity; Separated flows; square cylinder; Compressible fluid; Vortex shedding; Computational fluid dynamics; Bluff body; Digital simulation; Periodic oscillation; square cylinder; Oscillating flow; Morison equation; Large eddy simulation; Modelling; Vortex flow; Square section; Drag coefficient; Mesh generation; Turbulence structure
• ISSN: 0271-2091; 1097-0363
• DOI: 10.1002/fld.1881

The unsteady forces on a square cylinder in sinusoidally oscillating flows with non‐zero‐mean velocities are investigated numerically by using a weakly compressible‐flow method with three‐dimensional large eddy simulations. The major parameters in the analysis are Keulegan–Carpenter number (KC) and the ratio between the amplitude and the mean velocities of the approaching flow (AR). By varying the values of KC and AR the resulting drag and lift of the cylinders are analyzed systematically at two selected approaching‐flow attack angles (0 and 22.5∘). In the case of the non‐zero attack angle, results show that both the drag and lift histories can be adequately described by Morison equations. However, Morison equations fail to correctly describing the lift history as the attack angle is zero. In addition, when the ratio of AR/KC is near the Strouhal number of the bluff‐body flow, the resulting drag is promoted due to the occurrence of resonance. Based on the results of systematic analyses, finally, the mean and inertia force coefficients at the two selected attack angles are presented as functions of KC and AR based on the Morison relationships. Copyright © 2008 John Wiley & Sons, Ltd.